pqc/external/flint-2.4.3/arith/divisor_sigma.c
2014-05-24 23:16:06 +02:00

88 lines
2.3 KiB
C

/*=============================================================================
This file is part of FLINT.
FLINT is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
FLINT is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with FLINT; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
=============================================================================*/
/******************************************************************************
Copyright (C) 2010 Fredrik Johansson
******************************************************************************/
#include "arith.h"
#include "fmpz.h"
/* note: destroys factors! */
void
_arith_divisor_sigma(fmpz_t res, const fmpz_factor_t factors, ulong k)
{
slong i;
fmpz * p;
fmpz_t r;
fmpz_one(res);
if (factors->num == 0)
return;
fmpz_init(r);
if (k == 0)
{
for (i = 0; i < factors->num; i++)
{
fmpz_set_ui(r, factors->exp[i] + UWORD(1));
fmpz_mul(res, res, r);
}
return;
}
else
{
for (i = 0; i < factors->num; i++)
{
p = factors->p + i;
fmpz_set(p, factors->p + i);
fmpz_pow_ui(p, p, k);
fmpz_pow_ui(r, p, factors->exp[i] + UWORD(1));
fmpz_sub_ui(r, r, UWORD(1));
fmpz_sub_ui(p, p, UWORD(1));
fmpz_divexact(p, r, p);
}
_fmpz_vec_prod(res, factors->p, factors->num);
}
fmpz_clear(r);
}
void
arith_divisor_sigma(fmpz_t res, const fmpz_t n, ulong k)
{
fmpz_factor_t factors;
if (fmpz_is_zero(n))
{
fmpz_zero(res);
return;
}
fmpz_factor_init(factors);
fmpz_factor(factors, n);
_arith_divisor_sigma(res, factors, k);
fmpz_factor_clear(factors);
}